Zener diodes are some of the most extensively-used components in semiconductor technology, and they are used for a wide variety of applications, including voltage regulation and protection from electrostatic discharge events. Two different kinds of current may affect the operation of a Zener diode at breakdown: impact ionization (or avalanche breakdown) current; and tunneling (or Zener breakdown) current. The term “Zener diode” as it is classically used, and as it will be used herein, refers to a diode in which tunneling breakdown and avalanche breakdown occur simultaneously.
In power integrated circuit (IC) technology, the Zener diode is commonly integrated into a circuit and is in “discrete” form as a separate unit. In general, Zener diodes, especially when used in smart power technologies, should have both zero temperature coefficient (“zero TC”) and long term stability. Zero temperature coefficient means that the reverse breakdown voltage is substantially invariant with temperature, within a useful temperature range. Long term stability means that the reverse breakdown voltage and reverse leakage current do not change with time over the useful life of the device. Due to the zero TC and long term stability of Zener diodes, they are widely used in voltage clamping and reference. However, conventional Zener diodes suffer from substrate current injection when forward biased and when reverse biased. This substrate current injection may result in design difficulty because substrate current results in a differential between the anode terminal current and the cathode terminal current. More importantly, a high substrate current injected from the Zener diode(s) may also disturb operation of other devices that share the same semiconductor substrate as the Zener diode(s).